Periodontal diseases result from both bacterial plaque accumulation and host response to plaque microorganisms and their products. Several studies of the bacterial flora associated with periodontal disease have implicated Bacteroides gingivalis as an important pathogen in affected individuals. The proposed project will evaluate the potential of B. gingivalis to grow in subcutaneous chambers implanted in mice. The primary objective for developing a mouse subcutaneous chamber model for B. gingivalis is to more closely define the interactions between the organism and the host throughout the disease process. The murine abscess model currently employed by several investigators for studying B. gingivalis infection is limited in its ability to examine the host response to infection. Strains of B. gingivalis previously characterized as invasive or noninvasive in the murine abcess model will be examined for their ability to grow in mouse subcutaneous chambers. Chamber fluid will be removed at appropriate time points for bacteriological culture, microscopic examination and assay of immune products. Interactions of bacteria with specific phagocytic host cells and the histological development of the intrachamber lesion will be examined using cell specific reagents. Total immunoglobulin, B. gingivalis specific antibodies and secondary mediators of inflammation will also be quantitated. The long term objective of this work is to combine the subcutaneous chamber model used for growth of B. gingivalis with the animal models of periodontal disease to begin to define the interplay between bacterial products and host defense factors. This may exemplify how the host- parasite interrelationship determines the disease status of the periodontium.